Reduction of slack in metal coil slitting lines

ABSTRACT

The application discloses the reduction of slack in metal coil slitting lines, wherein a relatively wide strip is passed through a slitting instrumentality by which it is slit into a plurality of narrower strips which are then recoiled by a common recoiling device. Because of variations in thickness across the width of the original strip, the recoiled narrower strips which are being rewound simultaneously, will have various degrees of slack, resulting in some loose coils. According to the invention, an electrostatic fluidized bed is disposed between the slitting device and the recoiler, below the slit strips. The bed contains a suitable powder, such as mica; and as any one of the slit strips sags toward the fluidized and charged bed, it picks up some of the charged powder particles. The pick-up is proportionate to the amount of sag, or proximity of the sagging strip to the bed. The picked up powder is trapped in the wraps of the strip on the recoiler, effectively thickening the wrap, and thus restores tension and results in taking up the slack. The system is self-compensating and automatic.

United States Patent Ketterer REDUCTION OF SLACK IN METAL COIL SLITTING LINES [52] US. Cl. 72/46, 72/129 [51] Int. Cl B21b 45/00, B2lf 11/00 [58] Field of Search 72/46, 129, 183; 83/22,

[56] References Cited UNITED STATES PATENTS 3,443,307 5/1969 Werner 72/46 Primary Examiner-Richard .l. Herbst Assistant Examiner-Robert M. Rogers Attorney, Agent, or Firm-John W. Melville; Albert E. Strasser; Stanley H. Foster [11] 3,826,120 [451 July 30, 1974 [57] ABSTRACT The application discloses the reduction of slack in metal coil slitting lines, wherein a relatively wide strip is passed through a slitting instrumentality by which it is slit into a plurality of narrower strips which are then recoiled by a common recoiling device.- Because of variations in thickness across the width of the original strip, the recoiled narrower strips which are being rewound simultaneously, will have various degrees of slack, resulting in some loose coils. According to the invention, an electrostatic fluidized bed is disposed between the slitting device and the recoiler, below the slit strips. The bed contains a suitable powder, such as mica; and as any one of the slit strips sags toward the fluidized and charged bed, it picks up some of the charged powder particles. The pick-up is proportionate to the amount of sag, or proximity of the sagging strip to the bed. The picked up powder is trapped in the wraps of the strip on the recoiler, effectively thickening the wrap, and thus restores tension and results in taking up the slack. The system is self-compensating and automatic.

4 Claims, 1 Drawing Figure REDUCTION OF SLACK IN METAL COIL SLITTING LINES BRIEF SUMMARY OF THE INVENTION It is common practice today to slit relatively large master coils longitudinally so as to produce a plurality of narrower coils to specific dimensions which may be required by subsequent operations such as roll forming or press feeding. The standard practice is to place the master coil on a pay-off reel and feed the leading edge through a rotary slitting device and thence onto a rewind reel. The several narrower strips are rewound simultaneously separated only by thin spacing tools mounted on an overarm separator or by separating pans. The rewinding machine imparts the same angular velocity to the smaller coils even though there may be a variation in material thickness as a result of the original rolling process. Sometimes the original relatively wide strip is thicker toward the middle and thinner near the edges, or vise versa. In either case, after several revolutions, the variation in thickness causes a different tension on the rewind and varies the tightness of the several coils. The net effect is to produce more slack in the infeed material between the rewinder and the slitting coils for those strips which are thinner. This error of course accumulates and causes loose wound coils unless some compensation is applied.

There are at least two common methods of handling this problem. One is to use a so-called tensioner which is inserted between the rewinder and the slitter and applies uniform tension to each strip regardless of its thickness. This simply moves the slack to a point between the tensioner and the slitter and requires the use of a pit to house the full accumulation of slack. It also means that the slack strips are not being pulled through the knives, since only the tight strips are being pulled. This causes inaccuracies in slitting. Aside from the disadvantages mentioned above, the tensioner provides a relatively expensive solution.

Another practice which is less expensive, is to insert pieces of cardboard intermittently and manually into the rewind reel at those points where the slack is excessive. This is of course an extremely hazardous procedure in that a man's hand can readily be caught and wrapped into the coil. A further disadvantage resides in the fact that the paper interleaves are shipped with the coil to the end user; and if allowed to be further processed with the steel, they can cause damage to dies and roll forming machinery. Furthermore, on light gauge material particularly the paper itself can deform the metal which is coiled.

The present invention overcomes the disadvantages described above in a simple and relatively inexpensive and substantially self-compensating and automatic way. An electrostatic fluidized bed of conventional construction (which in itself forms no part of the present invention) is disposed between the slitting device and the recoiler below the slit strip and extending across the entire width of all the slit strips. The strip itself is grounded. Thus, as one or more of the slit strips sags to a greater or lesser degree, it attracts particles of electrostatically charged powder from the fluidized bed and these particles cling to the particular strip. The amount of powder attracted depends upon the proximity of the strip to the fluidized bed, or in other words upon the amount of sag of the particular strip. Thus, the more a strip sags, the more powder will be attracted and deposited on it and carried foward to the rewinding instrumentality where it is trapped in the wraps of the strip as it is being rewound. The powder effectively thickens the wrap of the particular strip and thus restores tension and results in taking up the slack.

Since the amount of powder picked up is in direct proportion to the amount of sag, the system is automatic and self-compensating.

BRIEF DESCRIPTION OF THE SINGLE FIGURE OF THE DRAWING The FIGURE of the drawing is a diagrammatic representation of a slitting line showing the invention.

DETAILED DESCRIPTION In the drawing, a slitter is indicated diagrammatically at 10. A recoiling device is indicated diagrammatically at 11. The horizontal line 12 represents the passline of a tight strip. The broken line 13 represents a slack strip. An electrostatic unit is diagrammatically indicated at 14. This may be a so-called electrostatic cloud coater manufactured by The Electrostatic Equipment Corporation. The electrostatic cloud coater is a conventional device and in and of itself does not form a part of the present invention. It comprises a plenum chamber and a plate in the upper'portion upon which the powder is deposited and an electrostatically charged grill through which the powder moves and by which it is electrostatically charged. Above the electrostatic cloud coater 14 is provided a hood 15 connected to an exhaust system to collect excess powder.

The parameters of the location of the electrostatic cloud coater with respect to the strip 12 will depend of course upon the distance between the slitter 10 and the recoiler 11, the speed of passage of the strip, the particular powder used in the fluidizing device, and the like. By way of example, in a situation where the distance between the centerline of the slitter l0 and the centerline of the recoiler 11 was twenty feet, the centerline of the electrostatic cloud coater was disposed substantially at the midpoint therebetween. The electrostatic unit was positioned so that a tight strip would be eight inches away from the bed. At this distance, a very thin coating of powder was obtained and a heavier coating was attained as the strip sagged. The .strip was run at approximately three hundred to four hundred feet per minute. The air flow in the fluidizing apparatus was about seven cubic feet per minute. The grill was charged with fifty kilovolts and the strip was grounded. The particular powder used was No. IOO-K Dry Ground Mica obtained from US. Mica Company. Both fifteen and sixteen gauge material was run through the apparatus and the width of the slit strips was four and one-half inches.

Both with fifteen gauge and sixteen gauge material, after several minutes of coating, the strips were tight and no further sagging occurred. However, the thicker material took slightly longer to become tight.

As to the choice of powder, mica is an excellent material for this purpose since it is relatively inexpensive and abundant so that it is readily available. However, other materials may be used provided they behave well electrostatically, are not corrosive to the metalbeing slit, are readily removable from the strip if desired for later operation, and if the powder'is allowed to remain on the slit coils it should be lubricative in nature.

It is also interesting to note that as the individual strip is tightened, it moves faster and therefore picks up less powder, further adding to the automatic character of the operation.

It will be clear that various modifications may be made without departing from the spirit of the invention. No limitation not specifically set forth is therefore intended and none should be implied.

The embodiments of the invention in which an exclusive property or privilege is claimed are defined as follows:

1. In a metal slitting line, wherein a relatively wide strip is passed through a slitting instrumentality, whereby it is slit into a plurality of relatively narrower strips, which narrower strips are then recoiled on a common recoiling device, and wherein, as a result of variations in the thickness of the relatively wide strip across its width, one or more of the relatively narrower strips will sag to varying degrees more than others of said relatively narrower strips, resulting in some loose coils of the narrower strips, the improvement comprising: an electrostatic fluidized powder bed disposed about midway between said slitting instrumentality and said recoiling device, and below said relatively narrower strips, and extending entirely across the width of all said relatively narrower strips; whereby particles of electrostatically charged powder from said fluidized bed are attracted and cling to the sagging ones of said relatively narrower strips, in proportion to the proximity thereof to said bed as a result of the sagging, said particles clinging to said strips and being trapped in the wraps of the respective rewound strips, effectively increasing the thickness of the respective wraps, and taking up the sag in the respective ones of said relatively narrower strips.

2. The apparatus of claim 1, wherein said powder is non-corrosive, readily removable from the strips for subsequent operation, lubricative in nature if allowed to remain on the coiled strips, and electrostatically chargeable.

3. The apparatus of claim 1, wherein said powder is mica.

4. The method of reducing slack in a metal coil slitting operation wherein a relatively wide strip is passed through a slitting instrumentality to produce a plurality of relatively narrower strips which are then recoiled on a common recoiling device, and wherein, because of variations in thickness of the original strip across its width, the several relatively narrower strips sag to varying degrees; comprising passing said several relatively narrower strips over an electrostatic fluidized powder bed, whereby the individual strips will attract particles of said powder in an amount proportional to their proximity to said bed as a result of the degree of sag of the respective relatively narrower strips, said attracted powder being trapped in the wraps of the respectively narrower strips, whereby to increase effectively the thickness of the sagging strips in proportion to the degree of sag, and thus take up the sag of the respective relatively narrower strips. 

1. In a metal slitting line, wherein a relatively wide strip is passed through a slitting instrumentality, whereby it is slit into a plurality of relatively narrower strips, which narrower strips are then recoiled on a common recoiling device, and wherein, as a result of variations in the thickness of the relatively wide strip across its width, one or more of the relatively narrower strips will sag to varying degrees more than others of said relatively narrower strips, resulting in some loose coils of the narrower strips, the improvement comprising: an electrostatic fluidized powder bed disposed about midway between said slitting instrumentality and said recoiling device, and below said relatively narrower strips, and extending entirely across the width of all said relatively narrower strips; whereby particles of electrostatically charged powder from said fluidized bed are attracted and cling to the sagging ones of said relatively narrower strips, in proportion to the proximity thereof to said bed as a result of the sagging, said particles clinging to said strips and being trapped in the wraps of the respective rewound strips, effectively increasing the thickness of the respective wraps, and taking up the sag in the respective ones of said relatively narrower strips.
 2. The apparatus of claim 1, wherein said powder is non-corrosive, readily removable from the strips for subsequent operation, lubricative in nature if allowed to remain on the coiled strips, and electrostatically chargeable.
 3. The apparatus of claim 1, wherein said powder is mica.
 4. The method of reducing slack in a metal coil slitting operation wherein a relatively wide strip is passed through a slitting instrumentality to produce a plurality of relatively narrower strips which are then recoiled on a common recoiling device, and wherein, because of variations in thickness of the original strip across its width, the several relatively narrower strips sag to varying degrees; comprising passing said several relatively narrower strips over an electrostatic fluidized powder bed, whereby the individual strips will attract particles of said powder in an amount proportional to their proximity to said bed as a result of the degree of sag of the respective relatively narrower strips, said attracted powder being trapped in the wraps of the respectively narrower strips, whereby to increase effectively the thickness of the sagging strips in proportion to the degree of sag, and thus take up the sag of the respective relatively narrower strips. 